Theb is a multipurpose word. It can be used as virtually any part of speech (though the noun form is not very common). Grammatically it is very similar to how "fuck" is used, except theb can also be as a substitution for "reaction" words such as "neat" "cool" or "lol" etc. May also be used as a greeting or exclamation in certain contexts.
Theb isn't anything. It means whatever you want it to mean. It can be a verb, a noun, an adjective. It can mean extreme anger, happiness, sadness. It can be an expletive or an excited announcement. You choose depending on the circumstance.